Composite structures may be compacted and/or cured using vacuum bags that are placed over the structure and sealed. Reasonably good access to bag edges may be needed in order to allow the use of conventional bag sealants, however, such access may be problematic in certain layup configurations. For example, in the case of a cylindrically shaped skirt that is laid up over a dome-shaped part to form a cryogenic propellant tank, access to the relatively narrow gap in the throat of a Y-joint between the two parts may be limited. This limited access may make it difficult to fit relatively thin bag material into the gap and bring the bag edges out to a point on the layup where they can be conveniently sealed with a conventional bag sealant.
One solution to the problem involves using a pre-cured inner skirt wall tool as left-in-place tooling that is bonded to the dome using a paste adhesive. The structural plies of the skirt are then laid over skirt wall. The use of paste adhesives however, may not provide the desired performance for some applications, especially at cryogenic temperatures. Another solution to the problem involves filling the narrowest portion of the gap between the skirt and the dome with a wedge of honeycomb. The outboard surface of the honeycomb is hand trimmed to match the cylindrical face of a skirt tool which is butted up against the honeycomb wedge. This solution may also be undesirable because the presence of the honeycomb may make it difficult to dry-gas purge the joint of moisture prior to filling the tank with a propellant.
Accordingly, there is a need for a tool device and method for fabricating composite structures having joints forming narrow gaps, that reduce the need for hand fitting vacuum bags into the gap and which permit the use of conventional bag materials and sealants.